1. Technical Field
Some example embodiments relate generally to semiconductor integrated circuits, and more particularly, to nonvolatile memory devices and methods of operating nonvolatile memory devices.
2. Discussion of the Related Art
Semiconductor memory devices may be classified into volatile semiconductor memory devices and nonvolatile semiconductor memory devices. Volatile semiconductor memory devices may perform read and write operations at high speed, while contents stored therein may be lost when the devices are powered-off. Nonvolatile semiconductor memory devices may retain contents stored therein even when powered-off. For this reason, nonvolatile semiconductor memory devices may be used to store contents to be retained regardless of whether the devices are powered on or off.
Nonvolatile semiconductor memory devices may include a mask read-only memory (MROM), a programmable ROM (PROM), an erasable programmable ROM (EPROM), an electrically erasable programmable ROM (EEPROM), etc.
Flash memory is a commonly used type of nonvolatile memory device. Flash memory may be widely used for voice and image storing media in electronic devices, such as computers, cellular phones, personal digital assistants (PDAs), digital cameras, camcorders, voice recorders, MP3 players, handheld PCs, game machines, facsimile machines, scanners, and printers.
As the demand for high integration memory devices has increased, multi-bit memory devices having memory cells capable of storing multi-bit data have become more common.